Insulator structure



1932- c. LE G. FORTESCUE 1,873,7J50

INSULATOR STRUCTURE Filed Nov. 23. 1927 INVENTOR Char/es lefifEr/escue A'TTORNEY Patented Aug. 23, 1932 UNITED :STATES PATENT OFFICE 1 crmBLnsLeG. ronrnscua, or rir'rsnvaon, PENNSYLVANIA, ASSIGNOR T0 wEs'rmo 7 HOUSE ELECTRIC a VANIA nwsum'roa s'rauo'runr:

Applicationtlled November 23, 1927. Serial lio. 235,299.

My invention relates to insulator structures and particularly to means for connecting the members which carry the mechanical load m a high-voltageinsulator; i I

One object of my invention is to provide a structure of the above-indicated character which shall be free of the bonding-medium troubles of multi-part insulators heretofore employed. 1 a

Another objectof my invention is to provide an insulator which shall be mechanically and electrically stronger than former nsulators of similar type. a Another object of my invention is to provide an insulator which shall be moistureproof anddurable in construction.

Another object of my invention is to provide an insulator of die ectric and conducting materialswhich shall be integrally united in a manner similar to asolid body of one material. Another object of my invention is to so. unite the parts of a high-voltage insulator that utilizes substantially the full insulating value of the-air, orother medium in which the insulator is disposed, as to render such insulator of more practical and commercial form than similar insulators heretofore em-; ployed. Y I y, g

' Another object of my invention is to provide an insulatorin which the mechanical load forces shall be more uniformly distributed throughout the dielectric body and i between, the dielectric body and the metal terminal members, whereby the material shall be worked to substantially maximum efliciency, i

'Another object of my invention'is to provide a multi-part-insulator structure in which all of'the partsshall be sointimately united as to substantially preclude even the slightest relative displacement thereof under any, except destructive, mechanical and electrical forces to which they may be subjected, and in which the union between the parts Shall be substantially unafiectedby temperature changes. a I p Another object of my invention is to provide an insulator whichshall be simple in construction, economical to manufacture and effective in its operation.

In high-voltage-insulator Organic insulating materials, such as rubber, bakelite and compositions of various MANUFACTURING COMPANY, CORPORATION OF PENNSYL- ractice, pari tlcularly 1n COIQIIQCUOII, with lnsulatorsfor kinds, while lending themselves to many easy;

and desirable manufacturing advantages, arenot, and have not been, widely adopted in outdoor service for variousreasons, such as susceptibility to deteriorationfrom moisture and corona effects. r I

Inorganic or ceramic materials, such as porcelain glass, quartz and sillimanite, which are the weatherand corona-proof materials commonly employed, present many difliculties in manufacture, principally in con-- structing them of large mass and of ideal or desirable shapes and in bonding such materials to metal onto other members of the same or different dielectric nraterial. V

Neat Portland cement,v the commonly used medium for binding ceramic dielectric parts to each other and to metal parts, has several well-known disadvantages 1n insulator practice, such as requiring an expensive and time consuming steam-setting or curing process, having a troublesome reaction with moisture, and deteriorating with age.

Moreover, cement, as well as metal alloy or any of other bonding media that have beenemployed, so far as I am aware, do not cohere, but 'merely adhere, to the ceramic parts; I

Thefailure to effect cohesion has occasioned the necessity of many expedients to obtain insulators adequate for the service intended and has, in many instances, requiredthe insu'lators to be larger, heavier and more com plicated and expensive than they might otherwise have been. 3 y I c For instance, while the principle has been known for years that an insulator, in which the surfaces of the dielectric conform to the flow lines of the electrostatic field between insulating value of the air or other surrounding medium, mechanical stresses, weather effects, structural limitations, and other considerations have precluded the utilization of this principle to full practical advantage in outdoor insulators,

Practical insulators have employed the principle to relatively great advantage, by having the body surfaces and petticoats conform to the flow lines and equi-potential surfaces, respectively, ofthe electrostatic field between the terminals, but, by reason of the fact that the bonding media employed merely adhere and do not cohere to the parts united thereby, it has not been feasible to obtain an outdoor insulator that is practical, commercial and nearly theoretically perfect in accordance with the aforesaid p inciple.

Further, the previously known bonding media, in merely adhering to the dielectric parts, have not been capable of use under direct tension, and, in applications where a tension insulator might otherwise have been an exceedingly simple structure, the lack of cohesion of the bonding media has necessi tated a special design of the metallic and refractory parts to place the bonding media under compression, as in a suspension insulator of the ordinary cap-and-pin type, or in. an insulator where the metal and dielectric parts are disposed in interlocking or semiinterloclting relation.

In an insulator of another type, in which a portion of the dielectric body is in tension. the terminal members have been constructed for bonding over a considerable area of the longitudinal side surface of the dielectric member adjacent to the ends thereof, as in the case of an insulator embodying a dielectric rod, cylinder or tube, with metal end caps cemented thereto.

In such an insulator, the pulling or tension forces are substantially all concentrated in a relatively thin layer or zone of the dielectric material adjacent to the side surfaces, the central portion of a solid rod, thus connected, assuming very little of the load, as attested and illustrated by the fact that a tube is substantially as well adapted for this purpose as a solid rod of the same diameter. A diagram of the forces between the cap and the rod or tube of an insulator of the above type is, therefore, in the nature of a hyperboloid of revolution, with the crest of the curve, representing the weakest or zero force, at the center of the rod. From the center of the rod to the sides thereof, the forces at first increase slowly for a considerable dis tance away from the center, and then rapidly increase in a relatively narrow zone adjacent to the side surfaces.

The ideal tension rod is one in which the tension forces are all directed parallel to the longitudinal axis and are uniformly distributed throughout the cross-sectional area thereof but, to the best of my knowledge, none of the means heretofore employed for gripping, or attachment to, the end of a dielectric rod has been adapted to attain this result.

Thus, the mechanical stresses in tension insulators of the past have been concentrated and, in no structure, of which I am aware, have they been uniformly distributed, as between two flat plane elements disposed in direct compression normal to the plane surfaces thereof.

t is my aim to overcome the above-mentioned objections and to obtain an insulator which shall be free of moisture and other bonding-medium troubles, to make it possible for insulators to be constructed in closer con-- formity to the above-mentioned flow-line and equi-potential principle, to achieve a distribution of direct tension forces substantially as uniform as the distribution of compression forces between two fiat engaging members, to effect material economies in the construction of the parts, to provide stron er ensienal, torsional or other load-sustaining joints, and to produce, in brief, an insulator which shall be an improvement, in general, over other insulators in the field of service for which it is adapted.

Accordingly, in practicing my invention, I provide an insulator embodying two or more parts, one of which is essentially of dielectric material and the other either of dielectric material or metal, that are so molecularly integrally united, or caused to cohere, as to obtain the objects sought and to effect a bond or joint which is substantially as strong as the dielectric material adjacent thereto.

It has been found that chloro-platinic acid has an affinity for a ceramic or silica glaze or, at least, will become so intimately related thereto, if placed thereon and subjected to heat, as to provide a metallic surface which practically becomes a homogeneous part of the dielectric member. The union is so close that, when the metal coating is forcibly torn ofl of the porcelain member, particles of the porcelain are torn off with it.

The exact condition of the adjoining metallic and dielectric particles, thus brought together, is not known, but it is thought that softening of the silica glaze permits the platinum particles to become minutely interwoven, if not actually chemically combined, with the silica glaze to provide a joint which is materially tighter than is provided bet-ween two materials which merely adhere, or two materials which, while possibly capable of cohering, have been brought together in such manner as to cause mere adherence.

For instance, the deposition of the so-called sticky materials, the electrolytic deposition of metals, the spraying of molten metals, and other processes, do not ordinarily produce aurie bonds comparable instrength to the platin'ic acid silica glaze bond herein mentioned and which, tothe best of my knowledge, has never been employed as a load-sustaining joint in the insulator art asherein specified. a

The porcelain body has a math! or 'film ofceramic or silica-glaze thereon as t e result of the usual process of dipping the bodies in silica orsilicious glazing material and thereafter firing the same in akiln. In order prepare thesurface or surfaces for myv JOHN],

the same is coated with layers or films 18 of metallic glaze, and the porcelain. member again subjected to a firing operation, which may be at a temperature of approximately 750 C. after which it is slowly cooled to room temperature. The metallic glaze which I employ is preferably chloroplatinic acid suspended-in essential oils, such as lavender,

cloves and spice. The result is a lustrous,

silvery metallic surface which may be electroplated, soldered or otherwise treated or joined to other metal surfaces. I

When a metal surface is to be united with theporcelain member, a bonding medium such as ordinary solder, type-metal or other metal alloy .inay be placed therebetween in the molten state, completing the joint and uniting the entire structure in a substantially ho 2 n'iogeneous or molecularly integral mass, similar to a single massof one material, and having the ultimate tensional strength of the weakest materials-employed. Before apply; ing the bonding agent,thesurfaces may 2; tinned or otherwise treated, the dielectric and metallic bodies being, in general, susceptible of welding, soldering and other operations heretofore considered peculiar tometal bod: i'es only.

. Tests have indicated that, in contradistind tion to the heretofore-known electroplated, sprayed or'otherwise formed coafin s which merely adhere to the porcelain an may be peeled'thercfrom, the metallic glaze or films i cohere to thesilica glaze or ceramic films which,in turn, cohere to the porcelain. Attempts tov separate the metallic glaze from the porcelain result in tearing awaysurface particles of the porcelain from the porcelain body, showing that the metallic glam coheres to the porcelain with a strength substantially equalto the strength of the porcelain body, andywitha closeness comparable to the adjoining particles in a singlepiece ofporcelain. M

With such objects in view, aswell as other advantages Whichmaybe. incident to the utilization of the improvemenuthe invention consists in the parts and combinations hereinafter set forth and claimed, with theunderstanding that theseveral necessary elements constituting the samemay be variedin proportion, arrangement and texture without departing from the'nature and scope of the, invention.

Fig. 1 is a. view of an insulator'embodying thev invention and utilizingsubstantially the maximum insulating. value of air, Fig. 2 a view of a modified form of insulator embodying the invention and utilizing the mechanical and insulating values of a straight dielectric rodto substantially maximum advantage, andv i Fig. 3 isa detail view, similarto thetop central portion of-Fig. 2, of a modified form of the structurethereof. I Referring more specifically to the drawing the structure illustratedin Fig. 1 is similar to an ideal form of insulator set forth in Patent No. 1,129,520, issued Feb. 23, 1915 to K. C. RandalhS. W.'Farnsworth and myself, in which substantially the maximum insulating value of air or other surrounding medium may be utilizedby having the side surfaces of the dielectric'material of the'in v sulator conform to the electrostatic, tween the insulator terminals.

The structure illustrated in the abovementioned patent, while admirably adapted for indoor or laboratory use,has been ladversely afi'ected, for' practical outdoor or commercial use, by certain factors,-such as the weather, corona effects and bondingmedium troubles.

The weatherand corona eflects have practically required that the dielectric material shall be an inorganic material, which is, in general, difficult to- -fabricate and whichhas other limitations inimical to certain of the ideal'forms suggested by the patent.

The bonding media'known and employed up tothe time of the present invention are not of suflicient strength to permit their use under direct tension and, therefore, have required resort to various expedients, in tension in structed in accordance with the theory of Patent No. 1,129,520, may be obtained, as indicated in Fig. '1,in which metal 2 terminal members 34 and 35, indicated as having clevis and eye attaching portions 36 and 37, respectively, although other-suitable attaching portions may be employed, are also provided with oppositely disposed surfaces40 for attachment to an int'ermediate dielectric body 41' by my novel joint.

Inthis structure, the'connecting surfaces ularly integrally united, at every point of the abutting surfaces, to the dielectric body 41, the mechanical tensional stresses are thereby uniformly distributed throughout the dielectric body and extend in substantially straight lines parallel to the longitudinal axis of the insulator, so that, through out a transverse area equal to the projected transverse areas of the surfaces 40, the dielectric material is worked to maximum efficiency in tension.

Thus, without undercut, interlinked or mechanically interlocked parts, which are ordinarily considered necessary, a tension insulator is obtained which distributes the tensional forces substantially as well as compression forces are distributed between parallel-plane pressure members, and substantially the maximum strength of the materials is utilized under tension.

In the structure of Fig. 1, the side surfaces 12 of the insulating body 41 are flowline surfaces in the electrostatic field of the insulator, as determined by the surfaces 10; and rain sheds or petticoats 48 are provided, having surfaces conforming to equi-potential surfaces in this field.

In the form of my invention shown in Fig. 2, a straight dielectric bar or rod 45 is recessed at its ends, similarly to the manner in which the dielectric body 41 of Fig. 1 is recessed, for the reception of metal terminal members 46 and 47 which are secured to the bar 45 by my novel joint 25.

In accordance with aprior suggestion, the terminal members 46 and 47 may be provided with hood and toroidal members 49 and 50, respectively, of metal, or of dielectric material having adjacent metallic surfaces, to prevent arcing to the rod 45, to widely distribute the electrostatic stresses and to obtain other beneficial effects not particularly germane to this invention, except insofar as my invention renders such an insulator more effective. I

As shown in Fig. 3, in which corresponding parts are designated by corresponding reference characters, the end structure of the device shown in Fig. 2 may be modified by the substitution of a convex rounded end 52 on the bar 45 for the recessed end shown in Fig. 2 and by molecularly joining the hood 49 directly thereto, the hood may have, in turn, a metal terminal member 53 soldered or otherwise suitably secured thereto.

In the forms of my invention illustrated in Figs. 1, 2 and 3, the metal terminal members are merely placed against the dielectric bodies, in substantially abutting relation thereto, and held in position by my new joint, which assumes the load, in contradistinction to former joints which do not assume the entire load in direct tension, and in connection with which various expensive expedients must be employed as hereinabove pointed out.

IVhile I have described my preferred metal-glazing process as consisting of coating porcelain with a ceramic glaze which is, in turn, coated with chloro-platinic acid suspended in essential oils, and baked or fired at a temperature of the order of 750 C., it is possible to utilize, in general, a coating of any metal which is fired or otherwise treated to drive the metal molecules into intimate union, either molecular or atomic, with the porcelain or other dielectric material. Examples of other compounds or mixtures, which may be applied in a manner similar to chloro-platinic acid, are silver nitrate mixed with a reducing agent, such as sugar; silver oxalate; and copper acetate. If the metallic coating is susceptible of oxidation, as in the case of copper, the baking or firing may be effected in a reducing or non-oxidizing atmosphere.

By my invention, not only may insulators of old and tried forms be rendered more effective and free of former troubles, but a new and wider field is opened to progress, in a branch of the electrical industry which has, more than any other major branch, heretofore failed to develop in corresponding measure to the others.

I claim as my invention:

1. A strain insulator including a vitreous dielectric body, terminals for permitting said body to be subjected to mechanical tension, one of said terminals having a metallic surface, a metallic film over a portion of said body and integral with said bod said metallic surface substantially con orming to said metallic film and being soldered thereto, said film extending substantially normal to the line of tension whereby mechanical tension applied to said terminals tends to separate said metallic surface from said body.

2. A strain insulator including a vitreous dielectric body, terminals for permitting said body to be subjected to mechanical tension, one of said terminals having a metallic surface, a metallic film over a portion of said body and integral with said body, said metallic surface substantially conforming to said metallic film and being soldered thereto, said film extending substantially normal to the line of tension and being subject to all of the tension.

3. A strain insulator including a vitreous dielectric body, terminals for permitting said body to be subjected to mechanical tension, each of said terminals having a metallic sur face, metallic films disposed over portions of said bo y to be subjectedto mechanical ten said body and integral with said body between each of said metallic surfaces and said body, said metallic surfaces substantially conforming to said metallic films and being soldered thereto, said films extending substantially normal to the line of tension whereby mechanical tension applied to said terminals tends to separate said metallic surfaces from said body.

4. A strain insulator including a vitreous dielectric body, terminals for permitting said body to be subjected to mechanical tension, each of said terminals having a metallic surface gradually receding from the other, metallic films disposed over portions of said body and integral with said body between each of said metallic surfaces and said'body, said metallic surfaces substantially conforming to said metallic films and being soldered thereto, said films extending substantially normal to the lines of tension whereby me' chanical tension applied to said terminals tends to separate said metallic surfaces from said body.

5. A strain insulator including a one-piece vitreous dielectric body, a pair of one-piece terminals for permitting said body to be sub jected to mechanical tension, each of said terminals having a metallic surface, metallic films disposed over portions of said bod and integral with said body between eac of said metallic surfaces and said body, said metallic surfaces substantially conforming to said metallic films and being soldered thereto, said films extending substantially normal to the lines of tension whereby mechanical tension applied to said terminals tends to separate said metallic surfaces from said body. I

6. A strain insulator including a vitreous dielectric body having rounded terminalreceivin surfaces, terminals for permitting sion, each of said terminals having a rounded metallic surface, metallic films dis 'osed over said terminal-receiving portions 0 said body and integral with said body between each of said metallic surfaces and said body, said metallic surfaces substantially conforming to said metallic films and being soldered there to, said films extending substantially normal to the lines of tension whereby mechanical tension applied to said terminals tends to separate said metallic surfaces from said. bod

In testimony whereof, I have hereunto su scribed my name this 21st day of November,

1927. I CHARLES LEG. FORTESCUE. 

